Irises: Cleaning up beds

My bloom season is diminishing, so I am snapping off bloom stalks and off color foliage, and making sure that the ground under the new growth is loose and will not catch moisture. If a clump is very crowded it will need to be divided, but on some, I am just cutting out chunks of rhizomes and replanting rather than separating into individual rhizomes. Question: Is it best to wait for the 1 to 1 1/2 months recommended after bloom to divide the irises? Or if I divide now will they have more time to develop once they get to their new home?
Also, I am moving all lates to a separate bed, and also all rebloomers.